The present invention relates to tennis rackets and, in particular, to tennis rackets having a flexible section between the head and the handle.
A proper tennis swing requires the player to bring the tennis handle forward and allow its translational kinetic energy to be converted into rotational kinetic energy, that is, angular momentum. This whipping action causes the racket to be snapped about the wrist. A proper swing does not require the player to apply a torque through his wrist around the time of impact. Instead, the conversion of kinetic energy produces the whipping action without much effort at the time of impact.
By contrast, an incorrect swing uses excessive muscle energy at the wrist and elbow to push the racket through the swing. A result of this excessive muscle use is that a bending moment is applied to the shaft of the racket, and possibly causing pain and injury.
Known tennis rackets (U.S. Pat. No. 3,679,205) have employed a shaft that is hinged between the handle and the racket head. This known racket has a detent which causes the racket shaft to fold when an excessive bending moment is applied by a player who improperly swings the racket. The disadvantage with this known racket is the fact that the hinge point is significantly removed from the handle. Thus, the manual sensation caused by the folding of the racket is small.
Furthermore, this racket, once folded, does not return easily to its playing position. Thus, after one bad stroke, the player may not be able to recover. He may not have time to reassemble the racket.
The stiffness of the racket shaft has been unduly emphasized. Existing rackets are made very stiff to compensate for inaccuracies caused by a flexible shaft. As an accelerated racket shaft bends, the accuracy degrades as the angle between the handle and the racket face changes. The conventional approach to guard against these inaccuracies is to make the racket shaft stiffer. Consequently, important considerations such as the feel and biofeedback of a racket are sacrificed in search of greater stiffness.
Accordingly there is a need for a racket that is useful as a training device or a playing device and that has proper biofeedback without adversely affecting the accuracy of the racket.